In the case of mobile phone, the optimal resonant length for conventional resonant dipole antenna or patch antenna should be half of wavelength. If a wavelength is conducted according to the base band at 900 MHz, above wavelength is not implemental inside a cell phone. However, it could be overcome after a Planar Inverted-F Antenna is applied within. The Planar Inverted-F Antenna realizes an optimal resonant length with a quarter of wavelength mainly by using a shorting pin so as to place the antenna into the cell phone. However, when the shorting pin is applied, variations of resistances among the shorting pin are increased. That would narrow the bandwidth of the antenna down relatively. Therefore, metal shorting plate and metal shorting wall are designed for better bandwidth efficiency. At the same time, corresponding to the requirement of multi-frequency communication system, the surface of the Planar Inverted-F Antenna-is capable of being divided so as to divide an original complete resonant path into a plurality of resonant paths.
Alternatively, it could be conducted by extending the resonant paths in the way of extending conductor, or implementing the effect of multi-frequency and dividing-frequency by an arrangement for chip capacitors and inductors into the antenna.
In the view of the severe high bandwidth and low bandwidth requirements for dipole Planar Inverted-F Antenna, there are many improved structures provided. Please referring to FIG. 1, a conventional three-dimension view of the Planar Inverted-F Antenna is illustrated, the Planar Inverted-F Antenna comprises: a ground plane 13, a T-shape radiation metal element 14, a short-circuit (s/c) metal element 15, a coaxial transmit cable 16 and an adjutant metal pad 17, an s/c point 131 and a ground point 132 of the ground plane 13 close by an upside edge 133 of the ground plane 13. The T-shape radiation metal element 14 is located near the upside edge 133 of the ground plane 13. The T-shape radiation metal element 14 comprises: a first radiation element 141 substantially paralleled to the ground plane 13, a second radiation element 142 extending forward to an invert direction comparing with the first radiation element 141, a third radiation element 143, which is substantially vertical to the first radiation element 141 and the second radiation element 142, having a feed-in point 144.
The short-circuit metal element 15, formed as invert-L shape, is placed between the T-shape radiation metal element 14 and the ground plane 13. A centre conductor 161 of the coaxial transmit cable 16 is coupled to the feed-I point 132 of the third radiation element 143. The other ground conductor 162 is coupled to the ground point 132 of the ground plane 13. The adjutant metal pad 17 is electrically connected to the second radiation element 142. Above embodiment reaches the requirement of a transmission standard through combinations formed by modifications of the shape, length and width of the adjutant metal pad 17 and a corresponding location of the second radiation element 142 without increasing total size of the antenna.
However, the adjutant metal pad 17 is a C-shape piece and the modification must be conducted by bending whole metal pad, so that the adjutant process is not easy to execute. Therefore, the transmission bandwidth of its low-frequency base band is limited easily. In addition, the exactness for adjusting the length and width of the adjutant metal pad 17 is not easy to control. It must be consider as well the corresponding location of the adjutant metal pad 17 and the second radiation element 142. In conclusion, it's difficult to implement the production of the antenna and hard to accomplish the efficiency it claimed.